Many sites can modify the resin.properties and use
the standard resin.xml for configuration of their
servers, JVMs, clusters, and applications.
More complicated sites can modify the resin.xml
itself. The xml configuration file
resin.xml supports CDI custom services, EL expressions
and variables variables, imports and control structures.

Resin 4.0 introduced a number of new features and capabilities over
earlier versions of Resin. Along with these changes, configuration and
some operating semantics changed. Certain configuration was deprecated
and should be removed or rewritten using newer constructs.

Resin organizes resources and classloaders into nested environments.
Each environment context merges its own configuration with configuration
inherited from the parent environment. Each environment context: server,
host, web-app, etc. may be configured with any of the environment
configuration tags.